Abstract
The ribbons of the Ti45.3Ni54.7 shape memory alloy were prepared through the melt spinning technique. The study was focused on investigating the effect of the rapid solidification and grain size at characteristic start martensitic (Ms), final martensitic (Mf), start austenite (As) and final austenite (Af) transformation temperatures. Changes on martensitic transformation temperatures in Ti45Ni55 melt spun ribbons were observed as grain size is reduced. Results of optical microscopy and differential scanning calorimetry (DSC) were used to associate grain size with transformation temperatures.
Highlights
Shape memory alloys (SMAs) represent a unique class of materials that undergo a reversible phase transformation allowing these materials to display dramatic pseudoelastic stress-induced deformations and recoverable temperature-induced shape memory deformations
The reason why both R → B19’ and B19’ → B2 transformations are separated into two peaks which correspond to large and small grains, while the B2 ↔ R transformation is not separated into two peaks is that the B2 ↔ R transformation exhibits much smaller transformation strain than R → B19’ and B19’ → B2 transformations [6]
The differential scanning calorimetry (DSC) result showed that when wheel velocity increases from 30 m/s to 50 m/s the R-phase appears because the as-spun Ti45.3Ni54.7 ribbon has many Guinier-Preston (GP) zones, induced by the large number of defects
Summary
Shape memory alloys (SMAs) represent a unique class of materials that undergo a reversible phase transformation (martensitic transformation) allowing these materials to display dramatic pseudoelastic stress-induced deformations and recoverable temperature-induced shape memory deformations. Microsystems have been recognized as having the potential to revolutionize the performance of a wide range of products by merging silicon-based microelectronics with micromachining technologies, enabling complete systems-on-a-chip to be developed and allowing novel functionalities at reduced costs. In this context, the application of shape memory alloys for actuation of micropneumatic devices might bring a relevant technological breakthrough. SMA materials exhibit the highest energy density amongst current micro-electromechanical systems MEMS compatible materials and, more importantly, as size is reduced towards the micro-scale, they benefit from improved heat transport, which increases their response speed [2]
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